Abstract: The purpose of this proposal is to study the normal, experimentally-altered and regenerating cerebral microvasculature in vivo and cells derived from cerebral microvasculature in vitro in order to understand some of the specific factors that maintain its structural and functional integrity, lead to its orderly repair after injury, and to relate these studies to changes that occur in the "blood-brain barrier" during micro-vascular injury and repair. Specifically, we propose to 1) define some of the cellular and molecular events which occur during regeneration; 2) document the relationships between endothelium and blood elements and cells, smooth muscle and astroglia; 3) determine the sequence of reestablishment of barrier properties after injury and 4) delineate some of the special biochemical properties of the endothelium. The approach will utilize a variety of techniques and will seek to correlate and interrelate in vivo and in vitro observations.